The present invention relates to a portable radio terminal such as a pager and a mobile telephone.
In the prior art in order to minimize influence of noises generated from a liquid crystal display (LCD) used as a display means in a portable radio terminal, a shield is provided. However, with a recent advanced miniaturization of the portable radio terminal, the liquid crystal display and a radio unit have become located close to each other. Because of this, when the radio unit is in a condition of receiving a radio data, a processing for inverting an angle of orientation axis in a liquid crystal becomes a cause of a noise generation, with the result that a receiving sensitivity of the radio unit is deteriorated.
In order to overcome this problem, Japanese Patent Application Pre-examination Publication No. JP-A-04-281662 proposes to change a frame frequency of the liquid crystal display so as to reduce the noise to a transmission signal of a radio communication instrument. Alternatively, Japanese Patent Application Pre-examination Publication No. JP-A-02-141034 proposes a technology featured to stop the display in the liquid crystal display during a receiving period.
In JP-A-04-281662 however. even if the frame frequency is lowered, since the processing for inverting the angle of orientation axis in the liquid crystal is still required to be executed at a constant period, the influence to the radio unit is inevitable, and therefore, it is not possible to satisfactorily prevent the deterioration of the receiving sensitivity. In particular, in a receiving condition, since a signal having a very small level is received, a sufficient sensitivity is necessary, and therefore, it is greatly influenced by a noise attributable to the processing for inverting the angle of orientation axis in the liquid crystal.
In JP-A-02-141034, on the other hand, since the display is not carried out in the liquid crystal display during the receiving period, if the receiving period becomes so long to exceed the length of time which cannot be perceived by eyes of a human being, the display flickers to a seeing person, and therefore, becomes hard to see.
Accordingly, it is an object of the present invention to provide a portable radio terminal which has overcome the above mentioned problem of the prior art.
Another object of the present invention is to provide a portable radio terminal capable of avoiding the deterioration of the receiving sensitivity by preventing generation of the noise during a radio data receiving period, without flickering of the display in tie liquid crystal display.
The above and other objects of the present invention are achieved in accordance with the present invention by a portable radio terminal comprising:
a radio transmitting and receiving means for transmitting and receiving a radio data;
a memory means for storing a display data,
a control means receiving data received by the radio transmitting and receiving means, to generate a display data and to write the display data into the memory means;
a liquid crystal display means for visually displaying the display data; and
a display control means reading out the display data from the memory means for controlling the liquid crystal display means to cause the liquid crystal display means to visually display the display data, the display control means outputting a liquid crystal alternating signal to the liquid crystal display means at each time an image displayed in the liquid crystal display means is changed from one frame to a next frame, thereby to invert an angle of a liquid crystal in the liquid crystal display means,
wherein when a radio data receiving period overlaps the timing of outputting the liquid crystal alternating signal, the display control means defers the outputting of the liquid crystal alternating signal until the radio data receiving period ends, whereby the angle of the liquid crystal in the liquid crystal display means is not inverted until the radio data receiving period ends.
With this arrangement, when the radio data receiving period overlaps the time of outputting the liquid crystal alternating signal, since the timing for outputting the liquid crystal alternating signal is deferred until the radio data receiving period ends, it is possible to prevent generation of the noise caused because of the inversion of the angle of orientation axis in the liquid crystal, with the result that the receiving sensitivity is not deteriorated.
In an embodiment of the portable radio terminal, when the display control means defers the outputting of the liquid crystal alternating signal the display control means defers an outputting of a horizontal scan signal and a frame signal to be supplied to the liquid crystal display means.
In this embodiment, since not only the liquid crystal alternating signal but also the horizontal scan signal and the frame signal are deferred, it is possible to prevent a flickering of a displayed image which would have otherwise occurred by deferring the liquid crystal alternating signal.
In a preferred embodiment, radio transmitting and receiving means transmits and receives data in a time division system, and the display control means defers the outputting of the liquid crystal alternating signal by a length of time on the order of several milliseconds which corresponds to one receiving time slot.
In this embodiment, since the liquid crystal alternating signal is deferred by only the radio data receiving period (which is on the order of several milliseconds), the image sticking never occurs in the liquid crystal.
More preferably, the display control means defers the outputting of the horizontal scan signal and the frame signal by a length of time on the order of several milliseconds which corresponds to one receiving time slot.
In this case, since the horizontal scan signal and the frame signal are deferred by only the radio data receiving period (which is on the order of several milliseconds) the number of frames displayed in the liquid crystal display is never reduced to the degree which can be perceived by a human being, and therefore, the displayed image does not become hard to see.
Specifically, the control means ceaselessly updates the data stored in the memory means to a latest information, and the display control means reads the data from the memory means at the time of transferring the display data to the liquid crystal display means.
In this case, when the radio data receiving period overlaps the timing of changing from one frame to a next frame, the display of the next frame is deferred. However, since the data stored in the memory means is ceaselessly updated to the latest information by the control means and on the other hand the display control means reads the data from the memory means at the time of transferring the display data to the liquid crystal display, the data updated to the latest information is ceaselessly transferred to the liquid crystal display, with the result that the image displayed in the liquid crystal display is not deferred to the degree which can be perceived by a human being, and therefore, the displayed image does not become hard to see.
In the above mentioned portable radio terminal, the control means is configured to perform the function of the display control means. In this situation, the display control means can be omitted.
The above and other objects, features and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings.